Wireless Shared Spectrum Access Contention Based on Harq Feedback

1. A method comprising: at a first wireless device, receiving feedback signals from one or more second wireless devices, the feedback signals comprising acknowledgement (ACK) signals and negative acknowledgement (NAK) signals; computing a ratio of NAK/ACK signals in the feedback signals for a predetermined period of time; computing a duration of a clear channel assessment interval based on a first penalty function of the ratio of NAK/ACK signals; determining whether a wireless medium is free for the duration of the clear channel assessment interval by monitoring for wireless signals during the clear channel assessment interval before an extended clear channel assessment interval; if the wireless medium is determined to be free for the duration of the clear channel assessment, omitting the extended clear channel assessment interval and wirelessly transmitting data to at least one of the second wireless devices; and if the wireless medium is determined not to be free during the clear channel assessment interval, monitoring for wireless signals for a duration of the extended clear channel assessment interval that is uniformly randomly selected up to a maximum contention window and wirelessly transmitting the data to the at least one of the second wireless devices after determining that the wireless medium is free for the duration of the extended clear channel assessment interval, wherein the maximum contention window is computed as a second penalty function of the ratio of NAK/ACK signals.

2. The method of claim 1 , wherein computing the duration of the clear channel assessment interval comprises calculating a penalty function based on a monotonic function of the ratio of NAK/ACK signals.

3. The method of claim 1 , further comprising doubling the maximum contention window responsive to a detection of a wireless signal during the extended clear channel assessment interval.

4. The method of claim 1 , wherein the feedback signals are Hybrid Automatic Repeat request (HARQ) signals in a Long Term Evolution (LTE) system.

5. The method of claim 4 , wherein the first wireless device comprises an LTE evolved node B (eNB), and the HARQ signals are received from a plurality of user equipment (UE) devices associated with the LTE eNB.

6. The method of claim 4 , wherein the first wireless device comprises an LTE user equipment (UE) device, and the HARQ signals are received from an associated LTE evolved node B (eNB).

7. An apparatus comprising: a transmitter configured to wirelessly transmit data to at least one wireless device; a receiver configured to receive wireless signals on a wireless medium; and a processor configured to: receive feedback signals from the at least one wireless device via the receiver, the feedback signals comprising acknowledgement (ACK) signals and negative acknowledgement (NAK) signals; compute a ratio of NAK/ACK signals in the feedback signals for a predetermined period of time; compute a duration of a clear channel assessment interval based on a first penalty function of the ratio of NAK/ACK signals; determine whether the wireless medium is free for the duration of the clear channel assessment interval by monitoring for wireless signals during the clear channel assessment interval before an extended clear channel assessment interval; if the wireless medium is determined to be free for the duration of the clear channel assessment interval, omit the extended clear channel assessment interval and cause the transmitter to wirelessly transmitting data to the at least one wireless device; and if the wireless medium is determined not to be free during the clear channel assessment interval, monitor with the receiver for wireless signals for a duration of the extended clear channel assessment interval that is uniformly randomly selected up to a maximum contention window and cause the transmitter to wirelessly transmit the data to the at least one wireless device after determining that the wireless medium is free for the duration of the extended clear channel assessment interval, wherein the maximum contention window is computed as a second penalty function of the ratio of NAK/ACK signals.

8. The apparatus of claim 7 , wherein the processor is configured to compute the duration of the clear channel assessment interval by calculating a penalty function based on a monotonic function of the ratio of NAK/ACK signals.

9. The apparatus of claim 7 , wherein the processor is further configured to double the maximum contention window responsive to a detection of a wireless signal during the extended clear channel assessment interval.

10. The apparatus of claim 7 , wherein the feedback signals are Hybrid Automatic Repeat request (HARQ) signals in a Long Term Evolution (LTE) system, and the receiver is configured to receive the HARQ signals from a plurality of user equipment (UE) devices associated with the apparatus.

11. The apparatus of claim 7 , wherein the feedback signals are Hybrid Automatic Repeat request (HARQ) signals in a Long Term Evolution (LTE) system, and the receiver is configured to receive the HARQ signals from an LTE evolved node B (eNB) associated with the apparatus.

12. A system comprising: one or more first wireless devices configured to provide feedback signals, the feedback signals comprising acknowledgement (ACK) signals and negative acknowledgement (NAK) signals; and a second wireless device configured to: receive the feedback signals from the one or more first wireless devices; compute a ratio of NAK/ACK signals in the feedback signals for a predetermined period of time; compute a duration of a clear channel assessment interval based on a first penalty function of the ratio of NAK/ACK signals; determine whether a wireless medium is free for the duration of the clear channel assessment interval by monitoring for wireless signals during the clear channel assessment interval before an extended clear channel assessment interval; if the wireless medium is determined to be free for the duration of the clear channel assessment interval, omit the extended clear channel assessment interval and wirelessly transmit data to at least one of the first wireless devices; and if the wireless medium is determined not to be free during the clear channel assessment interval, monitor with the receiver for wireless signals for a duration of the extended clear channel assessment interval that is uniformly randomly selected up to a maximum contention window and cause the transmitter to wirelessly transmit the data to the at least one wireless device after determining that the wireless medium is free for the duration of the extended clear channel assessment interval, wherein the maximum contention window is computed as a second penalty function of the ratio of NAK/ACK signals.

13. The system of claim 12 , wherein the one or more first wireless devices comprise a plurality of Long Term Evolution (LTE) user equipment (UE) devices configured to provide the feedback signals as Hybrid Automatic Repeat request (HARQ) signals, and wherein the second wireless device comprises an LTE evolved node B (eNB) associated with the plurality of LTE UE devices.

14. The system of claim 12 , wherein the one or more first wireless devices comprise a Long Term Evolution (LTE) evolved node B (eNB) configured to provide the feedback signals as Hybrid Automatic Repeat request (HARQ) signals, and wherein the second wireless device comprises an LTE user equipment (UE) device associated with the LTE eNB device.